JK Academy Maharashtra Board Class 7 Science Solutions Chapter 6 Measurement of Physical Quantities
Balbharti Maharashtra State Board Class 7 Science Solutions Chapter 6 Measurement of Physical Quantities Notes, Textbook Exercise Important Questions and Answers.
Maharashtra State Board Class 7 Science Solutions Chapter 6 Measurement of Physical Quantities
Class 7 Science Chapter 6 Measurement of Physical Quantities Textbook Questions and Answers
Exercise
1. Write answers to the following questions in your own words:
(a) Why is the weight of the same object different on different planets?
Answer: The gravitational force that acts on the mass of an object is called its weight. Since the gravitational force on different planets is different, therefore the weight of the same object is different on different planets.
(b) What precautions will you take to make accurate measurements in day-to-day affairs?
Answer:
Following precautions will be taken to make accurate measurements in day to day affairs:
(i) The balance should carry the stamp of standardisation by the department of weights and measures.
(ii) Balance should be stable and the pointer of the balance should be upright.
(iii) The underside of the pan should not be tampered with any other weight or layers of other metal.
(iv) The weight should be made of metal.
(c) What is the difference between mass and weight?
Answer:
| Mass | Weight |
| 1. The amount of matter present in a substance is called mass. | 1. The gravitational force that acts on this mass is called its weight. |
| 2. It is a scalar quantity. | 2. It is a vector quantity. |
| 3. Mass remains same everywhere on the earth. | 3. Weight changes from place to place on the earth. |
2. Who is my companion?
Group ‘A’ Group ‘B’
(1) Velocity (a) litre
(2) Area (b) kilogram
(3) Volume (c) metre/second
(4) Mass (d) kilogram/cubic metre
(5) Density (e) square metre
Answer
Group ‘A’ Group ‘B’
(1) Velocity metre/second
(2) Area square metre
(3) Volume litre
(4) Mass kilogram
(5) Density kilogram/cubic metre
3. Explain giving examples.
(a) Scalar quantity
Answer: A quantity that can be completely expressed by its magnitude alone is called a scalar quantity. For example, only magnitude, i.e. a value with a unit, is used to express quantities such as length, breadth, area, mass, temperature, density, time, work, etc. Thus, we say that the length of a tunnel is two kilometres, the fever (temperature) is 101o Farenheit, etc.
(b) Vector quantity:
Answer: The quantity that is expressed completely only when magnitude and direction are both given is called a vector quantity. Displacement, velocity are vector quantities. For example, a displacement of 20 kilometres towards the north, the aeroplane flying at a velocity of 500 km/hr towards Mumbai.
4. Explain, giving examples, the errors that occur while making measurements.
Answer: The errors that occur while making measurements are:
1. Not using the appropriate device.
2. Not using the device properly.
For Example:
While buying things at grocery shops, the vegetable market, remember to look out for the following:
1. Does the balance carry the stamp of standardisation by the department of weights and measures?
2. Is the balance stable? Is the pointer of the balance upright?
3. Is the weight made of metal? How is the balance held?
4. Has the underside of the pan of the balance been tampered with?
5. Give reasons.
(a) It is not proper to measure quantities by using body parts as units.
Answer: As the body parts differ from person, the measurement will also differ. Therefore it is not proper to measure quantities by using body parts as units.
(b) It is necessary to get the weights and measures standardized at regular intervals.
Answer: Officers of the sub-division of Weights and Measures visit different places from time to time, and ascertain whether the weights and balances being used are proper or not. It is binding by law to use standard weights and measures. Therefore, it is necessary to get the weights and measures standardized at regular intervals.
6. Explain the need for accurate measurement and the devices to be used for that.
Answer:
(i) Measurement of substances that are precious, of great importance and used in very small quantities, is done meticulously and accurately.
(ii) Due to advancements in technology, devices that measure very small magnitudes of quantities like distance, mass, time and temperature, are available now, for example, distance and time in connection with very important sports competitions, mass of gold, body temperature, etc.
Project :
Collect information about various physical quantities used in day-to- -day life and the devices used for their measurement.